The purpose of this multicenter, placebo-controlled, randomized clinical trial is to evaluate the safety and tolerability of 10 mg oral alendronate, administered with or without a 1000 mg elemental calcium supplement daily, compared to the 1000 mg elemental calcium supplement in the treatment of postmenopausal women with osteoporosis by assessing spine and hip bone mineral density at baseline and at 3, 6, 12, and 24 months of treatment.